Programmable AC Source out of inverter and porgrammable DC power supply

[Michal Mytnik]

Hi,

since Programmable AC Sources are rather expensive, I was wondering if an idea of using Inverter (which is rather cheap) and supplying it with 12/24V from DC bench power supply and controlling DC current make any sense?
Any bright idea, someone tried that?

[Benta]

Won't work.
It would be a little like putting a dimmer on the mains wire to your TV to control the brightness.

[Emrys]

Hi Michal,
I don't think that setup would do what you're expecting. It's likely that reducing the current supply to the inverter will just cause it to stop working - but maybe if it was made cheaply enough, the output might scale with the input voltage (probably not).

The cheapest / easiest way to change AC voltage is to use a transformer, but that's a fixed solution.

You can use a VARIAC (basically a variable transformer) if you only want to vary the voltage and not the frequency.

It's possible to turn DC into AC, but it will require a significant amount of design + control & some pretty beefy power transistors / heat sinks (depending on the power you want to deliver). Basically you adjust the DC power to the level you want, then use an H bridge circuit to switch it on and off to your output. Just putting out a square wave will work ok in some applications, but you can improve that by adding dead time between the positive and negative states to make your signal look more sinusoidal.

I put together a quick simulation to show the basics, but you can probably find a ton of info online if you really want to go down the road of making your own AC supply.

[Michal Mytnik]

Thanks guys, was just curies, but guess you are right.

[Terry Bites]

That dimmer's been workin' for me bro.